This invention relates in general to gas detection devices and in particular to a new and useful method and device for testing a person's breath for the purpose of ascertaining the alcohol content of the breath and also the person's blood.
The known colorimetric test tubes for the analysis of the alcohol content in breath have a measuring range from 100 up to 3000 ppm. The lower sensitivity limit is determined by the reagent systems chromate/sulfuric acid on inert reagent carrier used for the alcohol test tubes (Test Tube Pocket Book, Air Testing and Technical Gas Analysis with Drager Tubes, page 32).
The breath alcohol content is determined from the blood alcohol content. For example, on the basis of the vapor pressure of alcohol over aqueous solutions, a blood alcohol concentration of 0.1% will yield a figure of about 250 ppm (.congruent.0.025% by volume). The lower sensitivity limit of the known test tube is already reached at a blood alcohol concentration of 0.05%, i.e. a breath alcohol concentration of about 125 ppm.